How can I use liquid caustic soda in making barsoaps

[Jones Rundora]

I make bar soaps using caustic soda flakes but this time around I bumped into liquid caustic soda. I have never used it and I have no clue on how to measure it according to the saponification value of the oils that I use.
Pleases guide me if it's possible to use liquid caustic soda in barsoaps. I normally use caustic soda flakes which I dissolve in water and the quantity is largely determined by the saponification value of the oil

 

[Picklekin]

I'm going to guess you mean you have some liquid sodium hydroxide solution, is that right? If so I would assume this is the same as making up a solution yourself, you just need to know the concentration.

Most lye calculators will have an option to use "masterbatch" lye solution, you just need to convert your lye concentration into a ratio usually (i.e. a 25% solution is a 1:4 ratio).

 

[DeeAnna]

The amount of lye solution that you would use is STILL determined by the saponification values and weights of the fats in the batch. That doesn't change.

What does change is the amount of water you add. There is water already in the liquid NaOH solution and you have to compensate for that. To know the amount of water in the liquid NaOH solution, you must first know the concentration of the solution.

NaOH solution used in manufacturing is usually 50% concentration. NaOH solution sold for use as a drain cleaner is often much weaker than that. If the concentration of the solution you have is much lower than about 25%, it will be difficult to use for making soap because it is too weak.

Here is the math to use --

NaOH solution = Weight solid NaOH / Solution concentration % X 100

Water in NaOH solution = NaOH solution weight - Weight solid NaOH

Weight of additional water = Total weight of water - Water in NaOH solution

Here is an example --

My recipe calls for 386 grams solid NaOH and 1170 grams water. I have an NaOH solution at 50% concentration. How much of the solution should I use and how much extra water do I need to add to make the soap?

NaOH solution = 386 grams / 50 X 100 = 772 grams

Water in NaOH solution = 772 grams - 386 grams = 386 grams

Weight of additional water = 1170 grams - 386 grams = 784 grams

 

[Jones Rundora]

I'm going to guess you mean you have some liquid sodium hydroxide solution, is that right? If so I would assume this is the same as making up a solution yourself, you just need to know the concentration.

Most lye calculators will have an option to use "masterbatch" lye solution, you just need to convert your lye concentration into a ratio usually (i.e. a 25% solution is a 1:4 ratio).

Thanks for the information and guidance.

The amount of lye solution that you would use is STILL determined by the saponification values and weights of the fats in the batch. That doesn't change.

What does change is the amount of water you add. There is water already in the liquid NaOH solution and you have to compensate for that. To know the amount of water in the liquid NaOH solution, you must first know the concentration of the solution.

NaOH solution used in manufacturing is usually 50% concentration. NaOH solution sold for use as a drain cleaner is often much weaker than that. If the concentration of the solution you have is much lower than about 25%, it will be difficult to use for making soap because it is too weak.

Here is the math to use --

NaOH solution = Weight solid NaOH / Solution concentration % X 100

Water in NaOH solution = NaOH solution weight - Weight solid NaOH

Weight of additional water = Total weight of water - Water in NaOH solution

Here is an example --

My recipe calls for 386 grams solid NaOH and 1170 grams water. I have an NaOH solution at 50% concentration. How much of the solution should I use and how much extra water do I need to add to make the soap?

NaOH solution = 386 grams / 50 X 100 = 772 grams

Water in NaOH solution = 772 grams - 386 grams = 386 grams

Weight of additional water = 1170 grams - 386 grams = 784 grams

Thank you for this detailed information , I am sure it will help me figure out how to move forward

 

[AliOop]

(i.e. a 25% solution is a 1:4 ratio).

Oops, a 25% lye solution is actually a 3:1 ratio, not 1:4.

It may be stated otherwise for different applications, but soapmaking calculators list the water first, then lye.

 

[Zany_in_CO]

I bumped into liquid caustic soda. I have never used it and I have no clue on how to measure it according to the saponification value of the oils that I use.

Majestic Mountain Sage has a calculator where you can input ready-made lye solution.

MMS Lye Calculator

If you have problems using the calculator you can contact the support team directly for assistance. They are always very helpful.

https://www.thesage.com/pages/contact